In recent years, there have been many electronic devices featured by keywords of light, thin, short, and compact, such as a mobile phone, an ultraslim liquid crystal TV and a plasma TV, and a lightweight notebook computer in the field of a semiconductor-related material. The high-density integration and high-density packaging or the like of electronic parts used therefor are progressing. Therefore, size reduction and higher density are required for a printed-wiring board or the like corresponding to the high-density packaging used for these electronic parts than ever before.
A multilayer printed-wiring board produced by a buildup system is often employed for the high density of the printed-wiring board. A thermosetting resin composition represented by an epoxy resin is ordinarily used for an insulating layer thereof. However, the thermosetting resin has a problem of internal stress accumulation caused by a decrease in free volume upon curing. Therefore, when the thermosetting resin is used as an insulating material of the printed-wiring board, cracks and warps may be generated in a molded product by cure shrinkage, and the reliability of the printed-wiring board may be decreased by the accumulation of internal distortion. Therefore, a curable resin composition having little accumulation of internal stress upon curing and generating few cracks has been aspired.
Because a mounting temperature is a high temperature of 250° C. or higher in a process of mounting a semiconductor device in a multilayer printed-wiring board when a semiconductor apparatus is produced after the curing of the resin, the warp of the multilayer printed-wiring board may be increased upon mounting. The moisture absorption of the resin is known to further increase the degree of the warp. Therefore, a resin composition generating few cracks upon curing and having an excellent low thermal expansibility and low water absorbability has been required.
Meanwhile, a cyanate ester resin has been known as a thermosetting resin having excellent heat resistance, a low dielectric constant, and low dielectric loss. Particularly, a resin composition using a bisphenol A-based cyanate ester resin and a bismaleimide compound in combination, as proposed in Japanese Patent Publication No. 54-30440 (Patent Literature 1), is referred to as a “BT resin.” The BT resin has an excellent electrical property, mechanical property, and chemical resistance or the like, and is used for an insulating layer of a multilayer wiring board. However, although the resin composition containing the bisphenol A-based cyanate ester resin has an excellent electrical property, mechanical property, and chemical resistance, the resin composition has a high water absorption rate. A further improvement in heat resistance or thermal expansibility of the resin composition has been required, and the development of cyanate ester resins having other structures has progressed.
For example, a novolac-based cyanate ester resin has been proposed in Japanese Patent Laid-Open No. 11-124433 (Patent Literature 2). However, a cured product using the novolac-based cyanate ester resin has a water absorption rate greater than that of the BT resin, which may lower heat resistance in moisture absorption.
Japanese Patent Laid-Open No. 2006-169317 (Patent Literature 3) discloses that a resin cured product using a triphenylmethane-based cyanate ester compound and a bismaleimide compound in combination has an excellent thermal expansibility. Furthermore, Japanese Patent Laid-Open No. 2006-143874 (Patent Literature 4) discloses that a resin cured product using a triphenylmethane-based cyanate ester compound and a novolac-based cyanate ester compound in combination has excellent water absorbability.